Fuel-cell installations or systems composed of high-temperature fuel cells are known, for example, from WO 2004/070858 A, U.S. Pat. No. 6,379,831 B1, and EP 1 271 684 A. In this case, the individual fuel cells are in the form of flat cells or tubes. Contact-making elements are provided between the cells and, in particular, are in the form of a mesh over an area. Vertical structures are also provided in WO 2004/070858 A. These structures are intended to be produced by folding of the mesh in predetermined directions in places, although this results in loss of flexibility. This adversely affects the long-term behavior of the contacts.
In the above prior art, contact strips can be used in order to make electrical contact with solid-ceramic fuel cells, connected in series or in parallel. Particularly in the case of tubular fuel cells, these contact strips are applied along a tubular fuel cell to the interconnector that is already provided there, and connect the cathode and anode of two individual fuel cells which are arranged one above the other (connected electrically in series). A plurality of adjacent fuel cells can be connected via one contact strip, in order to connect them in parallel (electrical connection in parallel).
Known contact-making elements which have been used in the past for electrical connection of tubular high temperature fuel cells are composed of nickel felt strips, which include a multiplicity of fine nickel fibers with a thickness of only a few tens of micrometers, and are therefore both flexible and compressible. In the compressed state, the nickel felt strips have a width of about 6 mm, and a height of 3 to 4 mm.
The height of the contact strip during its installation is governed by the distance which must be bridged by the contact between two cells. This is described in detail, for example, in EP 0 320 087 B1 and in EP 0 536 909 A1. For correct use, the nickel felts are adhesively bonded to the interconnector on the one hand and to the anode on the other hand, by means of a nickel paste. The paste is sintered at the operating temperature of the high-temperature fuel cells.
The production of the latter nickel felts is time-consuming, and associated with a large number of manufacturing steps. This incurs high costs. Furthermore, one undesirable characteristic of these contact strips is that the nickel felts can be resintered during long-term operation, so that the cell contact becomes rigid as a result of loss of flexibility and elasticity. This can result in individual contacts being torn off, and thus in the fuel-cell installation losing power, in the event of major temperature fluctuations.